1. Field of the Invention
The present invention relates to methods for manufacturing electro-optical device substrates and methods for manufacturing electro-optical devices, and more particularly, relates to a manufacturing technique of a reflection substrate, which is composed of a resin layer having surface irregularities and a reflection layer provided thereon, and of an electro-optical device.
2. Description of the Related Art
In some liquid crystal display devices, which is one type of an electro-optical device, a reflection layer for reflecting light is formed. This reflection layer is provided for forming a reflective liquid crystal display device in which an image formed in accordance with an optical state of the liquid crystal can be viewed using reflected light generated by reflection of external light. In addition, a transflective liquid crystal display device has been known which has a transflective layer formed by providing light transmitting portions in parts of a reflection layer and which is capable of performing both transmissive and reflective display.
When the reflection layer described above is formed to have an optically flat reflective surface, since incident external light is specularly reflected from the optically flat reflective surface, known problems may arise, for example, in that an observer is dazzled by reflection of illumination light, and that the visibility of a display screen is degraded by reflection of a surrounding scene thereon.
Accordingly, various techniques have been proposed in which reflected light is appropriately scattered by irregularities formed on a reflection surface of a reflection layer for suppressing or avoiding the above mentioned dazzle caused by illumination light and the reflection of a surrounding scene on a screen. For example, in a transflective liquid crystal display device, a glass having a frosted surface is formed by etching or the like, and a reflection layer made of a metallic aluminum thin film or the like is provided thereon, thereby forming a reflection surface having irregularities.
In addition, as another method for forming the reflection surface having irregularities described above, a method has been proposed which comprises the steps of applying a photosensitive resin onto a glass substrate, exposing and developing this photosensitive resin using a predetermined mask pattern to form a resin layer having irregularities or resin layers randomly dispersed, melting the resin layer(s) by heating so as to smooth the irregularities thereof to some extent, further applying an organic resin on the resin layer(s) so as to form relatively smooth surface irregularities, and then forming the reflection layer thereon.
However, according to the methods described above, since a surface having appropriate irregularities must be formed on an underlayer surface of the reflection layer, for example, etching conditions (such as the composition of an etchant and an etching time) for a glass substrate and/or heating temperature and time for the resin layer must be precisely controlled and adjusted. Accordingly, precise irregularities of the reflection surface are difficult to obtain with good reproducibility; hence, a two-stage etching process must be performed, or a resin layer having a two-layered structure must be formed in some cases. As a result, the manufacturing time is increased, and the manufacturing cost is disadvantageously increased.
In addition, when the distribution angle of scattering light determined by the irregularities of a reflection layer is not uniform, since external light cannot be efficiently used for display, problems relating to display quality may arise in some cases in that the displayed image is darkened, the brightness is abruptly changed at a specific angle, the viewing angle properties are substantially degraded, and the like.
Accordingly, the present invention was made to solve the problems described above, and an object of the present invention is to provide a manufacturing method of an electro-optical device substrate, in which irregularities on a reflection surface can be rapidly formed at a low cost as compared to the conventional method, and to provide a manufacturing method of an electro-optical device. In addition, another object of the present invention is to improve the display quality of a reflective display of electro-optical device as compared to the conventional method by improving the scattering properties of a reflection surface.